Conventional technology is known that detects changes to map data and implements updating (Japanese Patent No. 5315363, and Japanese Patent Application Laid-Open (JP-A) No. 2014-153236). In a road network analysis system described by Japanese Patent No. 5315363, probe information from plural probe cars is accumulated daily, and a change in traffic volume is computed for each road for each day. Then, when a road is detected for which there is a remarkable change in traffic volume before and after an identified reference day, it is determined that there has been a major road network change in that area that influences traffic, and that road is considered a change-related road. Next, routes between terminal points of plural change-related roads are searched for, routes with large overlaps between the found route and the change-related road are selected, and change-related roads and their terminal points are identified as related by being influenced by a single common cause. Thus, using changes in traffic volume and route searching to identify related locations enables survey route candidates to be effectively set for a possible field study of major road network changes.
In a road network analysis device described by JP-A No. 2014-153236, for specific portions constituting a road network, the traffic volume of vehicles passing through the portion is found from plural items of the probe information accumulated over a specific time period. A discontinuity incidence rate that is an incidence ratio of events in which vehicle positions become discontinuous is also found similarly. Changes in the road network are then detected based on the degree of change in the traffic volume and the degree of change in the discontinuity incidence rate between two different periods in the specific portions constituting the road network. If changes in the road network can be detected, these can be employed in road network surveys and the like.
A new road determination device described by Japanese Patent No. 2014-130529 performs map matching by identifying a travel path of a vehicle based on acquired probe information, and correcting the position of the vehicle to a position on the map when a link is present within a positional error range of the position of the vehicle on the travel path. Then, a travel path that could not be matched to a link in the map matching is extracted as a diverging path. Moreover, the extracted diverging path is determined to be a new road.
A map information generation system described by Japanese Patent No. 5029009 transmits travel path information as probe data to a map distribution center when a vehicle that is a probe car is travelling along a road not included in navigation map data. The map distribution center that has received the travel path information from respective vehicles accumulates the received data, and also groups together travel path information from travelling the same road and generates new road information related to one new road for each group.
The technologies described by Japanese Patent No. 5315363 and JP-A No. 2014-153236 mentioned above are methods of measuring traffic volumes within periods of given length on respective existing roads by associating probe information with road network information, and detecting changes in the road network from changes in traffic volume.
However, there is sometimes a need to carry out a repeat survey in order to determine sites at which change occurred, since changes in traffic volume accompanying changes to roads are highly likely to extend to roads in a range within the wider surrounding area.
Moreover, a road change can not necessarily be detected from traffic volume since traffic volume also arises from causes other than changes in roads (for example, the opening of a new commercial facility).
Moreover, the technology described by JP-A No. 2014-153236 mentioned above employs links in map data that are not continuous for information regarding passage of probe vehicles, and detects new roads with higher precision than when traffic volumes are employed alone. Although there is a possibility that the presence of new roads is detectable by this method, it is difficult to detect changes such as newly established pedestrian crossings or the installation of new signage by this method.
The technologies described in Japanese Patent No. 2014-130529 and Japanese Patent No. 5029009 mentioned above use probe vehicle travel paths on a map other than those of known links, vehicle speeds, and the like to detect new roads and to create map data. Again, although there is a possibility that the presence of new roads is detectable by these methods, it is difficult to detect changes such as newly established pedestrian crossings or the installation of new signage by these methods.
The present invention was arrived at in consideration of the above circumstances.